Ultrasonic transducer



HIGH

' VOLTAGE 8.6 76 58 F. J. FRY

uL'lRAsoNAIjC TRANSDUCER Filed De'c. 15. 1953 ,f 94 9 as L42 56 92 T 9496/5 JNVEN 0R.

FRANC/5 J FRY Arr'ys 2,863,075 ULrRAsoNrc rRANsDUcER Francis I. Fry,Champaign, Ill., assigner, by mesne assignments, to the United States ofAmerica as represented by the Secretary of the Navy Application December15, 1953, Serial N o. 398,441

i s Claims. (C1. 31o-8.1)

This invention relates to an ultrasonic transducer of the crystal typefor transmitting and receiving supersonic waves of Variable frequencies.

An important object of the invention isto provide an improvedelectromechanical, ultrasonic transducer for converting electricalvenergy at high frequencies in the supersonic range into mechanicalenergy.

A further -object of the invention is to provide an improvedconstruction using a piezoelectric crystal such as barium titanate as ameans for converting electrical energy with increased efficiency.

A still further object of the invention is to provide an ultrasonictransducer having a lens for focusing the sound beam in the chamber inwhich the liquid or other substance is subjected to `mechanicalkvibration by the highfrequency energy produced. y

A still further object of the invention is to provide a new and improvedclosure for separating the liquid enclosing the crystal from the chamberin-which liquid is contained in which mechanical vibrations areproduced. s

A still further object of the invention is in providing a removable lensat one side of thevibratory crystal for focusing sound in a liquid orchamber at the side of the crystal where the lens is mounted.

Other objects of the invention will appear in the specication and willbe more apparent from the accompanying drawings in which:

Fig. 1 is an elevation of the structure shown in section in Fig. 2 asapplied to a mounting plate and viewed from the right side of saidfigure; p Fig. 2 is a sectional view of anA ultrasonic transducerconstructed in accordance with the principles of the invention and astaken on the line 2 2 of Fig. l; and

Fig. 3 is an enlarged cross section of the lens and crystal portions asshown in Fig. 2.

This single-beam type of transducer may be used as a focusing irradiatorin a laboratory for producing lesions of small diameter but rather long.A multibeam transducer of this type is used as an essential part of aneurosurgical apparatus for laboratory use. With this apparatus, theeifects of ultrasound on the tissues of a central nerve system of ananimal or of a human being may be produced and studied.

Referring now more particularly to the drawings, a transducer inaccordance with this invention is secured by means of a mounting plateto one side of a receptacle to which the transducer is applied. Thisplate is of solid conducting material and has sets of peripheralopenings 12 and 14 by means of which it is secured to a container.

At the center of the plate 10 is an opening 16 with an inner bevelededge 18 and extending from the opposite face is an angular shouldergroove 20 extending around the opening. In this groove, a transducerring support 22 is seated having a plurality of shouldered machinescrews 24 inserted through the plate 10 from the inner latented Dec. 2,

side thereof and extending into the adjacent portion of the supportingring which projects inwardly around the edge of the opening 16. Theinner edge of the mounting ring within the opening 16 has a beveled face26 which corresponds to the beveled edge 18, and in which A is arectangular groove V28 for seating a ring retainer 30 for a lens 32. Thelens has a shoulder marginal piro-` jection 34, and the inner edge ofthe supporting ring 22 has a shouldered projection 36 for receiving thelens therein with the shouldered portion 34 abutting the projection 36.At the inner edge of the ring retainer 30 is a contact rim 38 forengaging the outer periphery of the lens 32 and, by means of the screws40 which extendv through the periphery of the ring 30 into the holdingring support 22, the lens is clamped tightly in position.

A compressible washer 42 may be interposed between the adjacent surfacesof the rings 30 and 22 so that the lens may be clamped tightly in placemaking a duid-tight joint and also permitting a compression of the ring30 against the edge of the lens. The lens is concave at its inner faceand may be of polystyrene or other suitable material. Y

The collar or mounting ring 22 has a cylindrical flange 44 to which anouter insulator 46 (Hysol 6020) is secured by machine screws 48, agasket 49 being clamped between the ring and the insulator. Theinsulator 46 has a bore 50 in which is closely itted a cylindricalmetallic conductor sleeve 52 having an outer flange 53 abutting theinsulator. The inner end of the sleeve 52 is countersunk at 54 toaccommodate a gasket 55. At

, the inner faces of the insulator 46 and sleeve 52 is a metalliccontact member 56 having a bore 58 of the same diameter as and coaxialwith the sleeve bore and having about the bore 58 a seriesvof threadedholes receiving screws 62 extending from the sleeve. A gasket 66 isseated in a groove 68 in the outer face of the contact member 56. Thusthe contact member 56 is vclamped against the insulator 456, sleeve 52,and sleeve gasket 55, and the gasket 66 is clamped against the innerface of the insulator.

The inner side of the contact member 56 diverges at 70 to a groove 72containing a ring gasket 74. The mounting ring 22 has a complementalgroove76 containing a ring gasket 78. A barium titanate `or othersuitable piezoelectric crystal 80, whose outer and inner faces aredesigned to provide minimum electrical stresses and are respectivelyplated with film electrodes 82 and 84, is clamped marginally between thegaskets 74 and 78 when the screws 48 are tightened. There is thus formedan annular chamber 86 adapted to contain an insulating liquid, such asoil, which may be supplied or removed through an opening 88 for which athreaded closure 90 is provided.

A conductor 92 extends from the outer end of the sleeve 52 forconnection to a high frequency high voltage. An outer conductor 94 isarranged with one tervminal clamped between the sleeve 52 and the gasket55 and with the other terminal clamped between the outer electrode 82and the outer gasket 74 and extending radially outward to a point aboutmidway of the radial contact distance between the electrode and thegasket 74. An inner conductor 96 is arranged with one terminal groundedto the collar 22 by a screw 100 and the other terminal clamped betweenthe inner electrode 84 and the inner gasket 78 and extending radiallyinward to a point about midway of the radial contact distance betweenthe electrode and the gasket. The conductor termnals engaging thegaskets 74 and`78 are thus held in good electrical contact with therespective electrodes 82 and 84 without interfering with the ability ofthe gaskets to seal oi`1c the oil chamber 86. l

The distance between the detachably mounted lens 30 and the electrode 84is about 0.010, and this space is filled with a good-sound-transmittingliquid, such as degassed water.

The crystal generates an ultrasonic beam at the high frequency of theapplied high voltage. In the absence of the lens 30, thebeam istransmitted unfocused to a liquid medium (not shown) at the right. If afocused beam is desired, the lens 30 is used.

This transducer will operate either in a vertical or horizontal positionas well as in any intermediate position. The transducer is thereforeparticularly designed for a exible ,fixed-frequency, ultrasonicinstrument for a wide range of research applications.

While a preferred embodiment has been described in some detail, itshould be regarded as an exampie or ernbodiment of the invention and notas a restriction or limitation therein as many changes may be made inthe construction and arrangement of the parts without departing from thespirit and scope of the invention.

I claim:

1. In an ultrasonic transducer, a pair of outer and inner annularclamping members having mutually facing outer and inner annular clampinggaskets, a piezoelectric disc crystal, film electrodes plated on thefaces of the crystal and marginally confronting the respective gaskets,means clamping the members toward each other to securely support thecrystal marginally, a retainer ring, a lens inward of the crystal andmarginally disposed between the ring and the inner clamping member, agood-sound-transmitting liquid film separating the lens from thecrystal, an annular gasket between the ring and the inner juncture ofthe lens with the inner clamping member, and means including the ringfor clamping the last-mentioned gasket against the juncture and clampingthe lens between the inner clamping member and the ring.

2. The structure of claim l, characterized in that the second clampingmeans is independent of the first-mentioned clamping means and isdetachable to enable the transducer to operate selectively with andwithout a lens.

3. The structure of claim l, characterized in that the two clampingmeans are detachable to enable different crystals and lenses to be usedand to enable the desired crystal to be used selectively with andwithout a lens.

4. In an ultrasonic transducer, a conductor sleeve, an annular insulatorembracing the sleeve, a ring inward of the sleeve and insulator, a firstannular gasket between the ring and sleeve, a second annular gasket,means clamping the ring to the inner faces of the sleeve and insulator,the first gasket between the ring and sleeve, and the second gasketbetween the ring and insulator, a conductor 4 collar having acylindrical portion extending inward from the insulator and surroundingand spaced radially from the ring, a third annular gasket between theinner face of the insulator and the outer end of the cylindricalportion, the collar having an inner end ange projecting toward thecollar axis, the ring and collar having axially spaced mutually facingouter and inner fourth and fifth annular gaskets, a piezoelectric disccrystal having parallel outer and inner faces respectively plated byfilm electrodes and arranged marginally between the fourth and fifthgaskets, means clamping the crystal to the fourth and fifth gaskets,whereby the insulator, ring, collar, crystal edge, and the second tofifth gaskets define an annular chamber for insulating oil, the chamberhaving an opening and a closure therefor, a conductor for connecting thesleeve to high frequency high voltage, a conductor clamped at one endbetween the sleeve and the first gasket and at its other end between thefourth gasket and the outer electrode, and a conductor grounded to thecollar and having a terminal clamped at one end between the innerelectrode and the iifth gasket.

5. The structure of claim 4, together with a soundconverging lensclosely spaced inward from the inner electrode and having an outerportion embraced by the fifth gasket and the ange, a film ofgood-sound-transmitting liquid in the space defined by the innerelectrode, the fifth gasket, and the lens, the ange having an annularinwardly facing ledge, the lens having an outwardly facing annularshoulder confronting the ledge, a retainer ring at the inner sides ofthe ange and lens, a sixth annular gasket at the inner juncture of theange with the lens, and means clamping the lens against the ledge, andthe sixth gasket against the juncture, whereby the lens is held in placeand the liquid film is sealed in place.

References Cited in the file of this patent UNITED STATES PATENTS2,430,013 Hansell Nov. 4, 1947 2,477,246 Gillespie July 26, 19492,484,014 Peterson Oct. 11, 1949 2,496,293 Kiernan Feb. 7, 19502,592,703 Jaffe Apr. 15, 1952 2,626,992 Holman Ian. 27, 1953 FOREIGNPATENTS 668,343 Great Britain Mar. 12, 1952 OTHER REFERENCES Ser. No.337,106, John (A. P. C.), published May 18, 1943.

UNTED STATES rATr/orricm Certicate of Correction Patent No. 2,863,075Franois'J. Fry

December 2, 1958 It ie hereby certified that error appears in the abovenumbered patent requiring Correction and that the said Letters Patentshould read as corrected below.

In the drawings, Figures 2 and 3 should appear as shown below instead ofas in the patent- F/G 2 48 44 l0 0 man 6 i@ vanaaf T" n 36 50 le 53 Q"40 Attest: KARL H. AXLNE, Attesting 0775091.

UNTED STATES PATENTAOFFICE Certieate of Correction Patent No. 2,863,075December 2, 1958 Francis J; "Fry It is hereby eertied "that errorappears in the above numbered patent requiring Correction and that thesaiel Letters Patent should read as corrected below.

In the drawlngs, Figures 2 and 3 should appear as shown below instead ofas in Eigned and sealed this 2nd day of June 1959.

Attest 2 KARL H. AXLNE,

ROBERT C. WATSON, Commissioner of Patents.

